You should go ahead and plant them now, do not prune them and water on regular basis until the soil is frozen solid. You can deadhead them if they still have flowers. With a temperature like that I think it is not important to use transplanting solution, but personally I would be looking at the potting soil they are using and try to unwrap the roots and clear the soil from the roots and mix it with your existing soil as plenty of the time growers are using water-retaining mixes which are bad during winter.

I agree would plant now. No pruning other than deadheading spent blooms if you wish. No need for transplanting solution. I’d also apply a 3 inch layer of straw mulch at the base. will help ensure get through winter ok.

One other thing you also mentioned bent branches. If the branches are actually damaged you can prune the damaged wood.

Sounds like you found good prices in the clearance section! Fall is a great time to plant hydrangeas and the temps you mentioned are just fine. I too see no need to prune (but do mulch) unless it is to remove dead wood or bent wood. The blooms can be deadheaded now or in Spring. They add some winter interest normally but depending on the shape of the shrubs, you may want to deadhead them now only this year and deadhead them in Spring in future years.

Where did you find these paniculatas?

You have gotten good advice above: plant now, mulch well (I use shredded bark since it is easier to source around me), and don’t let them dry out between now and freeze, but check soil a few inches down before watering. Panicled hydrangeas don’t like soggy soil. Only deadhead and prune to remove damaged wood.

In my area they bloom best with a good amount of sun, at least a half day, and most of mine are in all day sun. I am a bit cooler than you are, though.

Check relative sizes carefully from a reliable source such as the Missouri Botanical Garden’s PlantFinder since you have several types so you can plant the smaller ones where they will be easily seen.

http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.aspx

Just type in Hydrangea paniculata into the blank and hit search or enter and you will get a list of all the ones they grow. Searching by trade name doesn’t work well. IME MOBOT tends to be more accurate as far as size than plant tags, which often give size at 5 years, but many will continue to get larger over time.

Prices is why I like to check the clearance section!

Leungkitty, I went to the same sale and scored some lovelies as well, a twist n shout hydrangea 5g for $12, and it has stunning red leaves starting! Also bought 3 bobo’s to do a hedge as well. I can’t wait!